Haven't been active on the board for a while, but the thread title instantly drew me in. I have never, ever, seen the benefit of a temporary happiness boost. I am a micromanager, and I recognize my condition for what it is, and welcome any and all reductions to micromanagement in Civ. A temp happiness boost is an increase in micromanagement.
However, I never go for it because I simply don't see the payback. It is often that my cities aren't at their happy cap, so a boost does nothing for me (I don't play for points). Those cities at their cap are not always ready to grow to the next level (since I often stop pop as soon as I hit the cap), so my city may not even get the extra pop in time to benefit for long. Then, even if I can get some benefit from it, I have to keep an eye out for when the bonus expires so that I can starve out the unhappy peons.
Even during a long war I wouldn't have much incentive to go for the temp boost. I like permanent stuff. Or stuff that has an obvious, in-your-face benefit (e.g., a magical artifact that will help in the war but will disappear in ten turns).
I love the random events. They add a lot to the game. But, temporary happiness boost? Just not sexy.